A need has existed for many years for adequate and controlled greasing of rollable element bearings. Electric motors and other equipment operating at high rotational speeds accentuate this requirement because of operation at higher temperatures and loads which cause the grease to deteriorate more rapidly as well as to migrate out of the ball or roller track where it is needed. The trend in electric motor design is to use a smaller frame size for the same horse power or torque rating, which means higher operating temperatures and greater heat loss into the frame and into the bearing assembly. Also the trend is to use the smallest diameter bearing size that is possible to be used. These trends compound the problems for the requirements of adequate lubrication of the bearing assembly.
The prior art grease lubrication systems have failed to guarantee that fresh lubricant will be supplied onto the bearing raceway upon relubrication. The prior art greasing systems employed essentially a cylindrical cavity adjacent to the bearing unit, namely the rollable element such as balls, the cage for the balls, and the inner and outer races. This cylindrical cavity had a grease entry hole on the periphery of the cavity. The many problems that arose from this grease feed system where as follows:
1. The grease initially supplied into the cavity followed the path of least resistance. The grease might exit out a drain or along a cylindrical clearance around the shaft, at which point the operator usually stopped the regreasing because he saw the grease exiting and assumed the bearing was lubricated. PA1 2. The lack of initial grease coverage of all metal surfaces allowed rusting or corrosion to occur during shipment and storage even before the motor or machine could be put into initial use. This was especially a problem with shielded bearings which have an annular shield on one side of the bearing unit, usually affixed to the outer race, and disposed between the balls and the grease cavity. PA1 3. When the bearing was regreased, old oil-depleted grease base (soap) might be pushed into the bearing track and new grease might go only to the rear of the grease cavity. PA1 4. Upon regreasing the bearing unit, the new grease might flow behind old caked grease and out along the shaft with absolutely no grease being provided into the bearing unit and onto the inner and outer races. PA1 5. The lack of an inner grease cavity or reservoir in many prior art bearing assemblies limited the mounting position of the motor or machine to one with a horizontal shaft only.
The solution to the problem is to provide a grease lubricated bearing assembly wherein the new grease is directed axially toward the space between the rollable elements and not merely radially into a grease cavity nor merely axially toward a race of the bearing unit. This assures that the new grease is supplied to the space between the inner and outer races so as to relubricate the raceways and rollable elements. Grease cavities are provided on each axial side of the bearing unit and one of these cavities is provided with vane walls establishing radially directed vanes disposed closely adjacent the plane of the races of the bearing. These vane walls in conjunction with the revolution of the balls or rollable elements provide a slight pumping action to pump grease from that cavity in which the vanes are contained through the bearing unit into the opposite grease cavity.